It's a pretty good chunk of equity, but....
1k business users in 12 months seems pretty difficult - besides a good product you'll need marketing $$ or sales people to get you there - are they giving you any capital to get there?
You said they would be covering "initial expenses", but this sounds like you need to get your expenditures approved by the parent company, which seems not great.
If you're a technical person, this equity setup seems weird since you only have pretty indirect control of how well you can sell the product.
Given you're branching off from an existing startup and I assume taking their source code, will they be providing engineering support to help get people up to speed on the codebase, is there any expectation they will be kept in sync, will the new entity owe any royalties?
In the end, I think the question is: do you think the product/company is good? 5% of a great company is great, 5% of a shitty company is shitty. It sounds like the parent company basically doesn't know if this will work out or not and doesn't know the target country well, so it hoping you do.